INTEGRATED GEOPHYSICAL INVESTIGATION FOR GROUNDWATER POTENTIAL ASSESMENT OF GUANG RIVER CATCHMENTS, WEST GONDAR, ETHIOPIA

Abstract

The study area, Guang river catchments, in Amhara regional state, is found in Western Ethiopia and can be located at UTM coordinate between (195983-203777m) E and (1438974-1425310 m) N with an average elevation of 700 meters above sea level. The main objective of the research is to assess the groundwater potential of the Guang catchment using geophysical methods. This integrated geophysical investigation includes the electrical resistivity method (Vertical Electrical Soundings/VES), magnetic methods and Satellite gravity data). The Schlumberger electrode configuration with maximum current electrode separation (AB) of 600m from VES-1 up to VES-5 and 1000m from VES-6 up to VES-26 was used for the sounding survey. VES data on a total of twenty-six VES stations were collected using Schlumberger field array along six profiles. Three to five geoelectric layers are mapped in the geoelectric sections. The possible potential areas for groundwater production are that characterized by low resistivity values i.e. the weathered layer and fractured zone which have been identified as an aquifer. The magnetic survey was conducted across Guang river to map major E-W trending subsurface structures. From the total magnetic intensity data, the IGRF value is subtracted after the diurnal correction was applied. IGRF corrected data were enhanced by upward continuation and analytic signal filters to map structures that may act as a conduit for groundwater. Satellite gravity data taken from the International Gravimetric Bureau (BGI) gravity database was primarily aimed to map regional structures of the Guang and its surrounding catchments. The result of the gravity reconnaissance was used to plan a detailed integrated geophysical survey using Magnetic and electrical resistivity techniques (vertical electrical sounding).